Residual Pressure Test

Residual Pressure Test

Special tools, testers and auxiliary items required

• Brake pressure gauge 0-250 bar (VAG 1310A)

Make sure there is adequate brake booster pressure for this test.

Before starting

- Vehicle is raised on a twin post hoist.

Make sure that the brake system (master cylinder, brake hoses, brake lines and brake calipers) works properly and is free of leaks.

- Connect the Brake pressure gauge 0-250 bar (VAG 1310A).

Troubleshooting procedure if pads are worn on one side of the vehicle:

- Remove the bleeder valve at one of the front brake calipers. Connect the brake pressure gauge 0-250 bar (VAG 1310A).

- Start the engine.

Simulate brake applications at various pressures up to approximately 100 bar.

• Operate the brake pedal slowly at various pressures.

• Operate the brake pedal rapidly at various pressures.

- Firmly depress the brake pedal once as far as it will go.

If the wheel is difficult to turn and there is no residual pressure in the system:

- The pad may be sticking in the guide rail in the caliper, or the caliper may be dirty.

- The piston may be seized or sticking in the caliper.

If the wheel is difficult to turn and there is residual pressure in the system:

- The pedal mechanism may be sticking, or foreign bodies in the pedal mechanism.

- If it is possible to pull back the brake pedal slightly so that the brake pressure drops to zero, the brake booster must be replaced, or the pedal mechanism is sticking.

Checking the Brake Master Cylinder

- Connect the brake pressure gauge 0-250 bar (V.A.G 1310A) and build up a pressure of 5 to 10 bar without vacuum. Replace the brake master cylinder if the pedal yields continuously under this pressure.